Magnitude Error, Quadrature Modulation (QM)

In quadrature modulated (QM) systems, magnitude error refers to the difference between the ideal magnitude of the I/Q signal and the actual measured magnitude on a symbol-by-symbol basis. Magnitude error in QM systems causes the locus of symbol coordinates to either move away from the origin and expand or toward the origin and shrink. Magnitude error affects both the I and Q components simultaneously and can be either positive or negative, indicating magnitude gain or attenuation, respectively.